[1] : The Collaborative International Dictionary of English v.0.48

underwriter \un"derwrit`er\, n.
   one who underwrites his name to the conditions of an
   insurance policy, especially of a marine policy; an insurer.
   1913 webster

[2] : WordNet (r) 2.0

underwriter
     n 1: a banker who deals chiefly in underwriting new securities
          syn: investment banker
     2: an agent who sells insurance syn: insurance broker, insurance
        agent, general agent
     3: a financial institution that sells insurance syn: insurance
        company, insurance firm, insurer, insurance
        underwriter
see also:
investment banker insurance broker insurance agent general agent insurance company insurance firm 
insurer insurance underwriter 

[3] : Moby Thesaurus II by Grady Ward, 1.0

71 moby thesaurus words for "underwriter":
   accident insurance, actuary, annuity, approver, assurance,
   aviation insurance, bail bond, bailsman, bond, bondsman,
   business life insurance, casualty insurance,
   certificate of insurance, certifier, confirmer, cosignatory,
   cosigner, court bond, credit insurance, credit life insurance,
   deductible, endorser, endowment insurance,
   family maintenance policy, fidelity bond, fidelity insurance,
   flood insurance, fraternal insurance, godfather, godparent,
   government insurance, guarantee, guarantor, guaranty,
   health insurance, industrial life insurance, insurance,
   insurance agent, insurance broker, insurance company,
   insurance man, insurance policy, insurer, interinsurance,
   liability insurance, license bond, limited payment insurance,
   mainpernor, major medical insurance, malpractice insurance,
   marine insurance, mortgagor, mutual company, notary, notary public,
   ocean marine insurance, party, permit bond, policy, ratifier,
   robbery insurance, signatory, social security, sponsor,
   stock company, subscriber, surety, term insurance, theft insurance,
   upholder, warrantor

[4] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

underwriter, insurances. one who signs a policy of insurance, by which he 
becomes an insurer. 
     2. by this act he places himself as to his responsibility, in the place 
of the insured. he may cause a re-insurance q.v. to be made for his 
benefit; and it is his duty to act with good faith, and, without quibbling, 
to pay all just demands against him for losses. marsh. ins. 45, 

Underwriter >> U Words
Underwriter, definition of term: Underwriter
underwriter_pag1.html